# Semiconductor_Mos Capator
* # Three cases at semiconductor surface

### When I=0, dE/dx =0,i.e.,Fermi level is flat:

| Accumulation case |Depletion case| Inversion case |
| -------------- | -------------- | ----------------- |
| |||
| | | |

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* # Surface Depletion Region

* ### The figure shows the energy band diagram at surface of a p-type semiconductor.


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* # Charge in the semicinductir versus applied voltage

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* # Maximum depletion width

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* # Ideal MOS curve

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* # SiO2-Si MOS capacitor

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# Summary Of MOS Capacitor

* ### At the SiO2 interface, there are "3 possible charge distribution":

| Accumulation|Depletion| Inversion |
| -------------- | -------------- | ----------------- |
| |||

### The inversion is most important distribution, because it relates to the conducting channel for MOSFET operation.

* ### We have considered the characteristics of an ideal MOS capacitor. For a practical silicon MOS capacitor,the work function difference is generally not zero and there are various charges in the oxide or at the SiO2-Si interface that will affect the ideal MOS characteristics.

* ### Tunneling is the most important conduction process in SiO2. Tunneling current will generate defects in SiO2.When defects become dense enugh to form a continuous chain connecting the gate to the channel, catastrophic breakdown will occur.